Using a Parameter in a Bash Alias/Function

Question

I am trying to create a helpful bash alias/function. I can't seem to get it to properly interpret the string parameters.

alias phpr="php -r '${*}'"
alias decode="php -r 'echo base64_decode($1);'"

function phpr ()
{
    php -r "${*}"
}

function decode ()
{
    php -r "echo base64_decode($1);"
}

an example of how Im trying to use decode and it failing:

decode "MT0xO2JhbGFuY2VfaXNfc2hvd249MDtiZXRfYW1vdW50PTE7YmV0X3R5cGU9MTE7ZmF2b3JpdGVfdHJhY2sxPUZSRTtmYXZvcml0ZV90cmFjazI9TU1BO2Zhdm9yaXRlX3RyYWNrMz1UQU07ZmF2b3JpdGVfdHJhY2s0PU1FRDtmYXZvcml0ZV90cmFjazU9QVFVO3dhZ2VyX3N0YXR1cz0wO2N1cnJlbnRUcmFjaz1GUkU7Y3VycmVudFJhY2U9NjtyYWNlRGF0ZT0yMDExLTA0LTI4O3JhY2V1cGRhdGVkPTs%3D"

PHP Warning:  base64_decode() expects at least 1 parameter, 0 given in Command line code on line 1
PHP Stack trace:
PHP   1. {main}() Command line code:0
PHP   2. base64_decode() Command line code:1

I'm not sure when I'd use a function vs an alias for cases like these.

Tim · Accepted Answer · 2011-04-29 01:18:43Z

3

For your alias - alias doesn't take parameters. Have you tried alias phpr="php -r"?

For the function - it could be something being parsed in your string. Double-quotes allow parsing, Single-quotes take the string verbatim. You want the $1 to be parsed, but include any whitespace, wo you want double-quotes around that. But you can do single quotes for the rest of it:

function decode ()
{
    php -r 'echo base64_decode('"$1"');'
}

Note that this includes 4 single-quotes and 2 double-quotes.

EDIT Updated with Glenn's change. If php needs the parameter to be in quotes, you may need to do:

function decode ()
{
    php -r 'echo base64_decode("'"$1"'");'
}

Note that this includes 4 single-quotes and 4 double-quotes.

Ah, shell scripting...

edited Apr 29, 2011 at 1:18

answered Apr 28, 2011 at 22:04

Tim

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4 Comments

glenn jackman Over a year ago

you probably need some double quotes for the php script: php -r 'echo base64_decode"'"$1"'");' -- if $1 is 'foo bar', then you get php -r 'echo base64_decode("foo bar");'

Tim Over a year ago

ah, good point @glenn. I don't use php, so I'm not familiar with its needs. I've updated my answer.

Brombomb Over a year ago

Thanks @Tim. It works perfectly. It gives me insight into how to do the phpr one too (encapsulating the ' in ")

Tim Over a year ago

@Brombomb, when writing shell scripts, it's important to know the differences between the three escape mechanisms, and to remember that the quotes are simply toggles - you can enter and exit quote mode as many times as you want in a single line. Full details would be a much longer post. I'm pretty sure I've seen it documented somewhere. If I find the page, I'll link it here.

Oliver Charlesworth · Accepted Answer · 2011-04-28 22:00:16Z

0

I can answer one part of your question straight away: Bash aliases cannot take arguments.

answered Apr 28, 2011 at 22:00

Oliver Charlesworth

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1 Comment

Brombomb Over a year ago

So then that'd be the use case between alias and function. Thanks

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